Adult ICU patients will be eligible to be included in this study if they are expected to require enteral feed via a nasogastric or nasojejunal tube or established percutaneous jejunostomy for at least 5 days. Practically, this will be achieved by screening ventilated patients as they will require enteral feeding Major exclusion criteria include contraindications to ketogenic feeds, contraindications to enteral feeding, a new (< 5 days) percutaneous jejunostomy.